I have a 1.8T A6 Avant 1998. AEB engine, manual 5-speed, no mods. (this is a UK/Euro spec. car but should be similar to A4 models in US)
Bought the car with Audi warranty, but that's run out. They fixed a few problems for me but two remain unsolved, they kept giving me the 'your car is fine, Sir' line and I was too busy at the time to muscle my way to some proper service. Basically I was let down, and couldn't complain well enough!
Problem 1:
I have established that the front 'torque-stop' mount is bad. If I open the bonnet (hood) and drive along (in an empty car park!) the engine bobs up and down alarmingly. My gearstick moves back and forth on throttle inputs. This is quite a common failure, I now gather, but at the time of warranty Audi denied it was a problem, and I hadn't seen the engine movement. "They all do that, Sir".
Looking on some tech. sheets (ETKA, Bentley, erWin) I see that the mount is sited on the front cross-member, with a shaft that points back toward the engine. Bolted to the front of the engine there is a cylindrical casting. The rubber stop is in-between. (this may differ from A4's - where the female end is on the cross-member ??) Anyone got an easy way to fix this? Don't really want to drop the whole front off the car, but don't have a specific tech. sheet that covers!
I now find that the cross-member is actually a tube for the charge-air from the turbo to the intercooler. Is this right? If so, is it possible that the constant movement from the mount may crack the metal, causing charge-air leaks? I keep telling myself that VW would design out such a weak spot - but can't help thinking this may be a factor in my other problem.
Problem 2:
Sometimes get a misfire from cold for about 20-30 secs. Anyhow, the car simply lacks power up to 4000rpm, then seems to pull fine. Under load, there is definite hesitation here and there but it's difficult to feel because of problem 1! I have disconnected the N75 valve and felt the 'non turbo' difference, so it's not a specific boost loss caused by electronic safeguard. I have a VAG-COM and the car is throwing no fault codes! I have checked and tightened the knock-sensors and they seem to work fine.
I've seen many posts describing the nice turbo noise these engines produce. Mine is not so nice. It seems to be 'interrupted' and the rate of stutter seems to correspond with the hesitation I feel. There is no 'warble' or 'honk', indeed, one of the things Audi DID do was to replace the BPV.
I've been trawling for info on these problems for a while now, would really appreciate some pointers. Any website or book I could read? I'm not the worlds best mechanic, but my current situation predicts that I must now service this car myself, on a bit of a 'shoestring' budget! I'm just building myself a new garage and extending the house, so when that's done it'll be time to give my beloved vehicle some TLC. Gonna have a go anyway. I've had this car for three years now and I really want to enjoy full performance again.
Thanks for listening. Anyone who recognises these symptoms, or can help in any way, please get in touch!